The present application relates to batteries and battery packs, and in particular, to technologies ensuring safety and reliability of the batteries and the battery packs.
In recent years, electric vehicles (EVs) driven by electric motors have becoming increasingly popular. Usually, an electric vehicle uses a rechargeable secondary battery as an energy source for. A battery pack comprising multiple battery cells in a hard casing is mounted to a floor part of a vehicle body.
Typical battery cell packs used in electric vehicles employ a multitude (e.g., thousands) of individual battery cells organized in sub-units (sometimes referred to as modules or bricks) that are interconnected. The cells and modules are combined variously in series and parallel to provide sustained high-energy storage and output as desired for any particular application.
Conventional battery packs are usually comprised of rectangular shaped batteries closely packed in a single container. Although these battery packs are compact, their thermal management is very challenging. As a result, these battery packs are deficient in reliability and safety: if one battery cell that catches on fire (by short circuit, over charge, or overheating for example), it can quickly go out of control to inflame other battery cells in the battery pack.
Some conventional battery packs employ serpentine cooling tubes to guide cooling water to remove heat from the batteries, but these types of cooling systems are bulky and different to package in the battery system. Any leakage in the cooling conduit can produce disastrous result of circuit short. Some other conventional battery packs utilize air circulation to cool the batteries, but these systems may spread a local fire across the whole system.
Accordingly, there is a need for improved temperature control and safety for battery packs.